1. Field of the Invention
The present invention relates to a method of producing integrated electrodes in plastic dies containing cavities, to plastic dies with integrated electrodes and to applications of the same.
2. Description of the Related Art
DE 35 37 483 describes a method for the formation of a multitude of plate-shaped metallic microstructured bodies by molding a microstructured tool with a non-conductive molding compound. Thus a negative mold of the microstructured tool is filled up with metal by electrodeposition. Then the negative mold is removed. A removable conductive material is applied to the front surface of the tool. During molding this conductive material is transferred to the regions of the molding compound which are in contact with the front surface of the tool.
In a variation of this method, the non-conductive molding compound which fills up the spaces in the microstructured tool may be fixed by a layer of a conductive molding compound. The conductive molding compound contacts and covers the whole front surface of the tool.
DE 40 10 669 describes a method for producing negative molds of plate-shaped microstructured bodies. The base structure of the patterned negative mold forms a coherent area which is covered with a layer of conductive material. This negative mold may be filled with a metal by electroplating. A layer of a thermoplastic resin which is covered with a thin film of a conductive material is used for producing the negative mold. A mold insert is pressed into the heat softened layer of the thermoplastic resin via the thin conductive film. After cooling the thermoplastic resin, the negative mold is separated from the mold insert.
During the stamping process the coherent film of conductive material is split at the front surface of the mold insert corresponding to the pattern of the microstructure. The regions of the conductive film on the front surface of the mold insert stick to the front surface. During stamping the other regions of the film are pushed to the base of the structure of the mold insert by the thermoplastic resin flowing into the cavities of the mold insert.
Pieces of the film may remain as tinsel on the side walls of the structure. If necessary, the tinsel is removed from the negative mold by a laborious cleaning procedure before the negative mold is electroplated with metal. After demolding, the regions of the front surface of the mold insert form the base of the structure of the negative mold. This base is covered with a coherent conductive film which is contactable at its edge.
The tinsel on the side walls and on the front surface of the negative mold comes from the conductive film which is imperfectly split during the stamping process. Some tinsel touches on the conductive layer at the base of the negative mold structure. This results in partially conductive side walls of the structure and the directed deposition of metal in the negative mold is disturbed. Defects, cavities and thicker regions of the metal layer are thus created in the metallic microstructured body molded by electroplating.
The conductive film preferably consists of gold, copper, silver and alloys thereof or of carbon. A film like that on the coherent area of the base of the structure is suitable as an electrode for the electrodeposition of other metals, e.g., copper or nickel. This film is less suitable for the electroless deposition of these metals.